The present disclosure relates to a printed temperature sensor based on a resistor with negative temperature coefficient (NTC).
A thermistor is a type of resistor whose resistance has a particular dependence on temperature. When the dependence is known, the resistance can be used as a measure for the temperature. Temperature sensing circuits commonly use a thermistor of the NTC type where its resistance decreases as temperature rises since they provide a sufficiently linear dependence of resistance with temperature. NTC materials used for such thermistor typically comprises a ceramic material. However such materials require special ceramic substrates (alumina, quartz) that can withstand the sintering processes at more than thousand degrees Celsius. Making a ceramic based NTC suitable for low temperature processing is difficult without negatively affecting its thermo-electrical properties. In general, current high reliability thermistors require high temperature processing which makes it unsuitable for printing on widespread substrates in electronics, e.g. plastics such as PEN/PET, rubbers such as silicones or polyurethanes, composites boards such as FR4, high temperature foils e.g. polyimide or glass.
It is thus desired to provide a printable temperature sensor with reliable thermo-electrical properties which can be directly applied to (flexible) substrates under temperature conditions compatible with common industrial and printed electronics substrates.